A primary optical unit and a photodetector unit are arranged on a side of a optical branching unit, on which primary terminals are arranged, and a lightconversion unit, which receives primary light, converts the primary light into secondary light, and emits the secondary light, is arranged on a side of the optical branching unit, on which secondary terminals are arranged, to enable guiding of the primary light from the primary optical unit to the lightconversion unit and guiding of the secondary light from the lightconversion unit to the photodetector unit through optical fibers.
